[unix-history] / sys / kern / kern_time.c

/*
 * Copyright (c) 1982, 1986, 1989 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	from: @(#)kern_time.c	7.15 (Berkeley) 3/17/91
 *	$Id$
 */

#include "param.h"
#include "resourcevar.h"
#include "kernel.h"
#include "proc.h"

#include "machine/cpu.h"

/* 
 * Time of day and interval timer support.
 *
 * These routines provide the kernel entry points to get and set
 * the time-of-day and per-process interval timers.  Subroutines
 * here provide support for adding and subtracting timeval structures
 * and decrementing interval timers, optionally reloading the interval
 * timers when they expire.
 */

struct gettimeofday_args {
	struct	timeval *tp;
	struct	timezone *tzp;
};

/* ARGSUSED */
gettimeofday(p, uap, retval)
	struct proc *p;
	register struct gettimeofday_args *uap;
	int *retval;
{
	struct timeval atv;
	int error = 0;

	if (uap->tp) {
		microtime(&atv);
		if (error = copyout((caddr_t)&atv, (caddr_t)uap->tp,
		    sizeof (atv)))
			return (error);
	}
	if (uap->tzp)
		error = copyout((caddr_t)&tz, (caddr_t)uap->tzp,
		    sizeof (tz));
	return (error);
}

struct settimeofday_args {
	struct	timeval *tv;
	struct	timezone *tzp;
};

/* ARGSUSED */
settimeofday(p, uap, retval)
	struct proc *p;
	struct settimeofday_args *uap;
	int *retval;
{
	struct timeval atv;
	struct timezone atz;
	int error, s;

	if (error = suser(p->p_ucred, &p->p_acflag))
		return (error);
	if (uap->tv) {
		if (error = copyin((caddr_t)uap->tv, (caddr_t)&atv,
		    sizeof (struct timeval)))
			return (error);
		/* WHAT DO WE DO ABOUT PENDING REAL-TIME TIMEOUTS??? */
		boottime.tv_sec += atv.tv_sec - time.tv_sec;
		s = splhigh(); time = atv; splx(s);
		resettodr();
	}
	if (uap->tzp && (error = copyin((caddr_t)uap->tzp, (caddr_t)&atz,
	    sizeof (atz))) == 0)
		tz = atz;
	return (error);
}

extern	int tickadj;			/* "standard" clock skew, us./tick */
int	tickdelta;			/* current clock skew, us. per tick */
long	timedelta;			/* unapplied time correction, us. */
long	bigadj = 1000000;		/* use 10x skew above bigadj us. */

struct adjtime_args {
		struct timeval *delta;
		struct timeval *olddelta;
};

/* ARGSUSED */
adjtime(p, uap, retval)
	struct proc *p;
	register struct adjtime_args *uap;
	int *retval;
{
	struct timeval atv, oatv;
	register long ndelta;
	int s, error;

	if (error = suser(p->p_ucred, &p->p_acflag))
		return (error);
	if (error =
	    copyin((caddr_t)uap->delta, (caddr_t)&atv, sizeof (struct timeval)))
		return (error);
	ndelta = atv.tv_sec * 1000000 + atv.tv_usec;
	if (timedelta == 0)
		if (ndelta > bigadj)
			tickdelta = 10 * tickadj;
		else
			tickdelta = tickadj;
	if (ndelta % tickdelta)
		ndelta = ndelta / tickadj * tickadj;

	s = splclock();
	if (uap->olddelta) {
		oatv.tv_sec = timedelta / 1000000;
		oatv.tv_usec = timedelta % 1000000;
	}
	timedelta = ndelta;
	splx(s);

	if (uap->olddelta)
		(void) copyout((caddr_t)&oatv, (caddr_t)uap->olddelta,
			sizeof (struct timeval));
	return (0);
}

/*
 * Get value of an interval timer.  The process virtual and
 * profiling virtual time timers are kept in the p_stats area, since
 * they can be swapped out.  These are kept internally in the
 * way they are specified externally: in time until they expire.
 *
 * The real time interval timer is kept in the process table slot
 * for the process, and its value (it_value) is kept as an
 * absolute time rather than as a delta, so that it is easy to keep
 * periodic real-time signals from drifting.
 *
 * Virtual time timers are processed in the hardclock() routine of
 * kern_clock.c.  The real time timer is processed by a timeout
 * routine, called from the softclock() routine.  Since a callout
 * may be delayed in real time due to interrupt processing in the system,
 * it is possible for the real time timeout routine (realitexpire, given below),
 * to be delayed in real time past when it is supposed to occur.  It
 * does not suffice, therefore, to reload the real timer .it_value from the
 * real time timers .it_interval.  Rather, we compute the next time in
 * absolute time the timer should go off.
 */

struct getitimer_args {
		u_int	which;
		struct	itimerval *itv;
};

/* ARGSUSED */
getitimer(p, uap, retval)
	struct proc *p;
	register struct getitimer_args *uap;
	int *retval;
{
	struct itimerval aitv;
	int s;

	if (uap->which > ITIMER_PROF)
		return (EINVAL);
	s = splclock();
	if (uap->which == ITIMER_REAL) {
		/*
		 * Convert from absoulte to relative time in .it_value
		 * part of real time timer.  If time for real time timer
		 * has passed return 0, else return difference between
		 * current time and time for the timer to go off.
		 */
		aitv = p->p_realtimer;
		if (timerisset(&aitv.it_value))
			if (timercmp(&aitv.it_value, &time, <))
				timerclear(&aitv.it_value);
			else
				timevalsub(&aitv.it_value, &time);
	} else
		aitv = p->p_stats->p_timer[uap->which];
	splx(s);
	return (copyout((caddr_t)&aitv, (caddr_t)uap->itv,
	    sizeof (struct itimerval)));
}

struct setitimer_args {
	u_int	which;
	struct	itimerval *itv, *oitv;
};

/* ARGSUSED */
setitimer(p, uap, retval)
	struct proc *p;
	register struct setitimer_args *uap;
	int *retval;
{
	struct itimerval aitv;
	register struct itimerval *itvp;
	int s, error;

	if (uap->which > ITIMER_PROF)
		return (EINVAL);
	itvp = uap->itv;
	if (itvp && (error = copyin((caddr_t)itvp, (caddr_t)&aitv,
	    sizeof(struct itimerval))))
		return (error);
	if ((uap->itv = uap->oitv) && (error = getitimer(p, uap, retval)))
		return (error);
	if (itvp == 0)
		return (0);
	if (itimerfix(&aitv.it_value) || itimerfix(&aitv.it_interval))
		return (EINVAL);
	s = splclock();
	if (uap->which == ITIMER_REAL) {
		untimeout(realitexpire, (caddr_t)p);
		if (timerisset(&aitv.it_value)) {
			timevaladd(&aitv.it_value, &time);
			timeout(realitexpire, (caddr_t)p, hzto(&aitv.it_value));
		}
		p->p_realtimer = aitv;
	} else
		p->p_stats->p_timer[uap->which] = aitv;
	splx(s);
	return (0);
}

/*
 * Real interval timer expired:
 * send process whose timer expired an alarm signal.
 * If time is not set up to reload, then just return.
 * Else compute next time timer should go off which is > current time.
 * This is where delay in processing this timeout causes multiple
 * SIGALRM calls to be compressed into one.
 */
realitexpire(p)
	register struct proc *p;
{
	int s;

	psignal(p, SIGALRM);
	if (!timerisset(&p->p_realtimer.it_interval)) {
		timerclear(&p->p_realtimer.it_value);
		return;
	}
	for (;;) {
		s = splclock();
		timevaladd(&p->p_realtimer.it_value,
		    &p->p_realtimer.it_interval);
		if (timercmp(&p->p_realtimer.it_value, &time, >)) {
			timeout(realitexpire, (caddr_t)p,
			    hzto(&p->p_realtimer.it_value));
			splx(s);
			return;
		}
		splx(s);
	}
}

/*
 * Check that a proposed value to load into the .it_value or
 * .it_interval part of an interval timer is acceptable, and
 * fix it to have at least minimal value (i.e. if it is less
 * than the resolution of the clock, round it up.)
 */
itimerfix(tv)
	struct timeval *tv;
{

	if (tv->tv_sec < 0 || tv->tv_sec > 100000000 ||
	    tv->tv_usec < 0 || tv->tv_usec >= 1000000)
		return (EINVAL);
	if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick)
		tv->tv_usec = tick;
	return (0);
}

/*
 * Decrement an interval timer by a specified number
 * of microseconds, which must be less than a second,
 * i.e. < 1000000.  If the timer expires, then reload
 * it.  In this case, carry over (usec - old value) to
 * reducint the value reloaded into the timer so that
 * the timer does not drift.  This routine assumes
 * that it is called in a context where the timers
 * on which it is operating cannot change in value.
 */
itimerdecr(itp, usec)
	register struct itimerval *itp;
	int usec;
{

	if (itp->it_value.tv_usec < usec) {
		if (itp->it_value.tv_sec == 0) {
			/* expired, and already in next interval */
			usec -= itp->it_value.tv_usec;
			goto expire;
		}
		itp->it_value.tv_usec += 1000000;
		itp->it_value.tv_sec--;
	}
	itp->it_value.tv_usec -= usec;
	usec = 0;
	if (timerisset(&itp->it_value))
		return (1);
	/* expired, exactly at end of interval */
expire:
	if (timerisset(&itp->it_interval)) {
		itp->it_value = itp->it_interval;
		itp->it_value.tv_usec -= usec;
		if (itp->it_value.tv_usec < 0) {
			itp->it_value.tv_usec += 1000000;
			itp->it_value.tv_sec--;
		}
	} else
		itp->it_value.tv_usec = 0;		/* sec is already 0 */
	return (0);
}

/*
 * Add and subtract routines for timevals.
 * N.B.: subtract routine doesn't deal with
 * results which are before the beginning,
 * it just gets very confused in this case.
 * Caveat emptor.
 */
timevaladd(t1, t2)
	struct timeval *t1, *t2;
{

	t1->tv_sec += t2->tv_sec;
	t1->tv_usec += t2->tv_usec;
	timevalfix(t1);
}

timevalsub(t1, t2)
	struct timeval *t1, *t2;
{

	t1->tv_sec -= t2->tv_sec;
	t1->tv_usec -= t2->tv_usec;
	timevalfix(t1);
}

timevalfix(t1)
	struct timeval *t1;
{

	if (t1->tv_usec < 0) {
		t1->tv_sec--;
		t1->tv_usec += 1000000;
	}
	if (t1->tv_usec >= 1000000) {
		t1->tv_sec++;
		t1->tv_usec -= 1000000;
	}
}
Commit	Line	Data
15637ed4 RG	1	/*
	2	* Copyright (c) 1982, 1986, 1989 Regents of the University of California.
	3	* All rights reserved.
	4	*
	5	* Redistribution and use in source and binary forms, with or without
	6	* modification, are permitted provided that the following conditions
	7	* are met:
	8	* 1. Redistributions of source code must retain the above copyright
	9	* notice, this list of conditions and the following disclaimer.
	10	* 2. Redistributions in binary form must reproduce the above copyright
	11	* notice, this list of conditions and the following disclaimer in the
	12	* documentation and/or other materials provided with the distribution.
	13	* 3. All advertising materials mentioning features or use of this software
	14	* must display the following acknowledgement:
	15	* This product includes software developed by the University of
	16	* California, Berkeley and its contributors.
	17	* 4. Neither the name of the University nor the names of its contributors
	18	* may be used to endorse or promote products derived from this software
	19	* without specific prior written permission.
	20	*
	21	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	22	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	23	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	24	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	25	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	26	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	27	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	28	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	29	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	30	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	31	* SUCH DAMAGE.
	32	*
78ed81a3	33	* from: @(#)kern_time.c 7.15 (Berkeley) 3/17/91
78ed81a3	34	* $Id$
15637ed4 RG	35	*/
	36
	37	#include "param.h"
	38	#include "resourcevar.h"
	39	#include "kernel.h"
	40	#include "proc.h"
	41
	42	#include "machine/cpu.h"
	43
	44	/*
	45	* Time of day and interval timer support.
	46	*
	47	* These routines provide the kernel entry points to get and set
	48	* the time-of-day and per-process interval timers. Subroutines
	49	* here provide support for adding and subtracting timeval structures
	50	* and decrementing interval timers, optionally reloading the interval
	51	* timers when they expire.
	52	*/
	53
78ed81a3	54	struct gettimeofday_args {
	55	struct timeval *tp;
	56	struct timezone *tzp;
	57	};
	58
15637ed4 RG	59	/* ARGSUSED */
	60	gettimeofday(p, uap, retval)
	61	struct proc *p;
78ed81a3	62	register struct gettimeofday_args *uap;
15637ed4 RG	63	int *retval;
	64	{
	65	struct timeval atv;
	66	int error = 0;
	67
	68	if (uap->tp) {
	69	microtime(&atv);
	70	if (error = copyout((caddr_t)&atv, (caddr_t)uap->tp,
	71	sizeof (atv)))
	72	return (error);
	73	}
	74	if (uap->tzp)
	75	error = copyout((caddr_t)&tz, (caddr_t)uap->tzp,
	76	sizeof (tz));
	77	return (error);
	78	}
	79
78ed81a3	80	struct settimeofday_args {
	81	struct timeval *tv;
	82	struct timezone *tzp;
	83	};
	84
15637ed4 RG	85	/* ARGSUSED */
	86	settimeofday(p, uap, retval)
	87	struct proc *p;
78ed81a3	88	struct settimeofday_args *uap;
15637ed4 RG	89	int *retval;
	90	{
	91	struct timeval atv;
	92	struct timezone atz;
	93	int error, s;
	94
	95	if (error = suser(p->p_ucred, &p->p_acflag))
	96	return (error);
	97	if (uap->tv) {
	98	if (error = copyin((caddr_t)uap->tv, (caddr_t)&atv,
	99	sizeof (struct timeval)))
	100	return (error);
	101	/* WHAT DO WE DO ABOUT PENDING REAL-TIME TIMEOUTS??? */
	102	boottime.tv_sec += atv.tv_sec - time.tv_sec;
	103	s = splhigh(); time = atv; splx(s);
	104	resettodr();
	105	}
	106	if (uap->tzp && (error = copyin((caddr_t)uap->tzp, (caddr_t)&atz,
	107	sizeof (atz))) == 0)
	108	tz = atz;
	109	return (error);
	110	}
	111
	112	extern int tickadj; /* "standard" clock skew, us./tick */
	113	int tickdelta; /* current clock skew, us. per tick */
	114	long timedelta; /* unapplied time correction, us. */
	115	long bigadj = 1000000; /* use 10x skew above bigadj us. */
	116
78ed81a3	117	struct adjtime_args {
	118	struct timeval *delta;
	119	struct timeval *olddelta;
	120	};
	121
15637ed4 RG	122	/* ARGSUSED */
	123	adjtime(p, uap, retval)
	124	struct proc *p;
78ed81a3	125	register struct adjtime_args *uap;
15637ed4 RG	126	int *retval;
	127	{
	128	struct timeval atv, oatv;
	129	register long ndelta;
	130	int s, error;
	131
	132	if (error = suser(p->p_ucred, &p->p_acflag))
	133	return (error);
	134	if (error =
	135	copyin((caddr_t)uap->delta, (caddr_t)&atv, sizeof (struct timeval)))
	136	return (error);
	137	ndelta = atv.tv_sec * 1000000 + atv.tv_usec;
	138	if (timedelta == 0)
	139	if (ndelta > bigadj)
	140	tickdelta = 10 * tickadj;
	141	else
	142	tickdelta = tickadj;
	143	if (ndelta % tickdelta)
	144	ndelta = ndelta / tickadj * tickadj;
	145
	146	s = splclock();
	147	if (uap->olddelta) {
	148	oatv.tv_sec = timedelta / 1000000;
	149	oatv.tv_usec = timedelta % 1000000;
	150	}
	151	timedelta = ndelta;
	152	splx(s);
	153
	154	if (uap->olddelta)
	155	(void) copyout((caddr_t)&oatv, (caddr_t)uap->olddelta,
	156	sizeof (struct timeval));
	157	return (0);
	158	}
	159
	160	/*
	161	* Get value of an interval timer. The process virtual and
	162	* profiling virtual time timers are kept in the p_stats area, since
	163	* they can be swapped out. These are kept internally in the
	164	* way they are specified externally: in time until they expire.
	165	*
	166	* The real time interval timer is kept in the process table slot
	167	* for the process, and its value (it_value) is kept as an
	168	* absolute time rather than as a delta, so that it is easy to keep
	169	* periodic real-time signals from drifting.
	170	*
	171	* Virtual time timers are processed in the hardclock() routine of
	172	* kern_clock.c. The real time timer is processed by a timeout
	173	* routine, called from the softclock() routine. Since a callout
	174	* may be delayed in real time due to interrupt processing in the system,
	175	* it is possible for the real time timeout routine (realitexpire, given below),
	176	* to be delayed in real time past when it is supposed to occur. It
	177	* does not suffice, therefore, to reload the real timer .it_value from the
	178	* real time timers .it_interval. Rather, we compute the next time in
	179	* absolute time the timer should go off.
	180	*/
78ed81a3	181
	182	struct getitimer_args {
	183	u_int which;
	184	struct itimerval *itv;
	185	};
	186
15637ed4 RG	187	/* ARGSUSED */
	188	getitimer(p, uap, retval)
	189	struct proc *p;
78ed81a3	190	register struct getitimer_args *uap;
15637ed4 RG	191	int *retval;
	192	{
	193	struct itimerval aitv;
	194	int s;
	195
	196	if (uap->which > ITIMER_PROF)
	197	return (EINVAL);
	198	s = splclock();
	199	if (uap->which == ITIMER_REAL) {
	200	/*
	201	* Convert from absoulte to relative time in .it_value
	202	* part of real time timer. If time for real time timer
	203	* has passed return 0, else return difference between
	204	* current time and time for the timer to go off.
	205	*/
	206	aitv = p->p_realtimer;
	207	if (timerisset(&aitv.it_value))
	208	if (timercmp(&aitv.it_value, &time, <))
	209	timerclear(&aitv.it_value);
	210	else
	211	timevalsub(&aitv.it_value, &time);
	212	} else
	213	aitv = p->p_stats->p_timer[uap->which];
	214	splx(s);
	215	return (copyout((caddr_t)&aitv, (caddr_t)uap->itv,
	216	sizeof (struct itimerval)));
	217	}
	218
78ed81a3	219	struct setitimer_args {
	220	u_int which;
	221	struct itimerval itv, oitv;
	222	};
	223
15637ed4 RG	224	/* ARGSUSED */
	225	setitimer(p, uap, retval)
	226	struct proc *p;
78ed81a3	227	register struct setitimer_args *uap;
15637ed4 RG	228	int *retval;
	229	{
	230	struct itimerval aitv;
	231	register struct itimerval *itvp;
	232	int s, error;
	233
	234	if (uap->which > ITIMER_PROF)
	235	return (EINVAL);
	236	itvp = uap->itv;
	237	if (itvp && (error = copyin((caddr_t)itvp, (caddr_t)&aitv,
	238	sizeof(struct itimerval))))
	239	return (error);
	240	if ((uap->itv = uap->oitv) && (error = getitimer(p, uap, retval)))
	241	return (error);
	242	if (itvp == 0)
	243	return (0);
	244	if (itimerfix(&aitv.it_value) \|\| itimerfix(&aitv.it_interval))
	245	return (EINVAL);
	246	s = splclock();
	247	if (uap->which == ITIMER_REAL) {
	248	untimeout(realitexpire, (caddr_t)p);
	249	if (timerisset(&aitv.it_value)) {
	250	timevaladd(&aitv.it_value, &time);
	251	timeout(realitexpire, (caddr_t)p, hzto(&aitv.it_value));
	252	}
	253	p->p_realtimer = aitv;
	254	} else
	255	p->p_stats->p_timer[uap->which] = aitv;
	256	splx(s);
	257	return (0);
	258	}
	259
	260	/*
	261	* Real interval timer expired:
	262	* send process whose timer expired an alarm signal.
	263	* If time is not set up to reload, then just return.
	264	* Else compute next time timer should go off which is > current time.
	265	* This is where delay in processing this timeout causes multiple
	266	* SIGALRM calls to be compressed into one.
	267	*/
	268	realitexpire(p)
	269	register struct proc *p;
	270	{
	271	int s;
	272
	273	psignal(p, SIGALRM);
	274	if (!timerisset(&p->p_realtimer.it_interval)) {
	275	timerclear(&p->p_realtimer.it_value);
	276	return;
	277	}
	278	for (;;) {
	279	s = splclock();
	280	timevaladd(&p->p_realtimer.it_value,
	281	&p->p_realtimer.it_interval);
	282	if (timercmp(&p->p_realtimer.it_value, &time, >)) {
	283	timeout(realitexpire, (caddr_t)p,
	284	hzto(&p->p_realtimer.it_value));
	285	splx(s);
	286	return;
	287	}
	288	splx(s);
	289	}
	290	}
	291
292	/*
293	* Check that a proposed value to load into the .it_value or
294	* .it_interval part of an interval timer is acceptable, and
295	* fix it to have at least minimal value (i.e. if it is less
296	* than the resolution of the clock, round it up.)
297	*/
298	itimerfix(tv)
299	struct timeval *tv;
300	{
301
302	if (tv->tv_sec < 0 \|\| tv->tv_sec > 100000000 \|\|
303	tv->tv_usec < 0 \|\| tv->tv_usec >= 1000000)
304	return (EINVAL);
305	if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick)
306	tv->tv_usec = tick;
307	return (0);
308	}
309
310	/*
311	* Decrement an interval timer by a specified number
312	* of microseconds, which must be less than a second,
313	* i.e. < 1000000. If the timer expires, then reload
314	* it. In this case, carry over (usec - old value) to
315	* reducint the value reloaded into the timer so that
316	* the timer does not drift. This routine assumes
317	* that it is called in a context where the timers
318	* on which it is operating cannot change in value.
319	*/
320	itimerdecr(itp, usec)
321	register struct itimerval *itp;
322	int usec;
323	{
324
325	if (itp->it_value.tv_usec < usec) {
326	if (itp->it_value.tv_sec == 0) {
327	/* expired, and already in next interval */
328	usec -= itp->it_value.tv_usec;
329	goto expire;
330	}
331	itp->it_value.tv_usec += 1000000;
332	itp->it_value.tv_sec--;
333	}
334	itp->it_value.tv_usec -= usec;
335	usec = 0;
336	if (timerisset(&itp->it_value))
337	return (1);
338	/* expired, exactly at end of interval */
339	expire:
340	if (timerisset(&itp->it_interval)) {
341	itp->it_value = itp->it_interval;
342	itp->it_value.tv_usec -= usec;
343	if (itp->it_value.tv_usec < 0) {
344	itp->it_value.tv_usec += 1000000;
345	itp->it_value.tv_sec--;
346	}
347	} else
348	itp->it_value.tv_usec = 0; /* sec is already 0 */
349	return (0);
350	}
351
352	/*
353	* Add and subtract routines for timevals.
354	* N.B.: subtract routine doesn't deal with
355	* results which are before the beginning,
356	* it just gets very confused in this case.
357	* Caveat emptor.
358	*/
359	timevaladd(t1, t2)
360	struct timeval t1, t2;
361	{
362
363	t1->tv_sec += t2->tv_sec;
364	t1->tv_usec += t2->tv_usec;
365	timevalfix(t1);
366	}
367
368	timevalsub(t1, t2)
369	struct timeval t1, t2;
370	{
371
372	t1->tv_sec -= t2->tv_sec;
373	t1->tv_usec -= t2->tv_usec;
374	timevalfix(t1);
375	}
376
377	timevalfix(t1)
378	struct timeval *t1;
379	{
380
381	if (t1->tv_usec < 0) {
382	t1->tv_sec--;
383	t1->tv_usec += 1000000;
384	}
385	if (t1->tv_usec >= 1000000) {
386	t1->tv_sec++;
387	t1->tv_usec -= 1000000;
388	}
389	}